kubernetes 1.8 源码分析之kubelet资源上报

最近在给k8s 1.8添加磁盘调度的时候，又撸了一遍k8s的相关的源码，之前看过我源码分析的那个是k8s 1.4版本的，1.8版本还是有点变化的。
先看看kubelet上报机制，这个是kubelet的心跳机制，定时上报节点状态，默认是10s，时间可以设定
在kubelet创建的时候就已经创建了节点状态的收集方法
pkg/kubelet/kubelet.go里面NewMainKubelet方法

klet.setNodeStatusFuncs = klet.defaultNodeStatusFuncs()

那默认的方法有哪些呢？

// defaultNodeStatusFuncs is a factory that generates the default set of// setNodeStatus funcsfunc (kl *Kubelet) defaultNodeStatusFuncs() []func(*v1.Node) error {    // initial set of node status update handlers, can be modified by Option's    withoutError := func(f func(*v1.Node)) func(*v1.Node) error {        return func(n *v1.Node) error {            f(n)            return nil        }    }    return []func(*v1.Node) error{        kl.setNodeAddress,        withoutError(kl.setNodeStatusInfo),        withoutError(kl.setNodeOODCondition),        withoutError(kl.setNodeMemoryPressureCondition),        withoutError(kl.setNodeDiskPressureCondition),        withoutError(kl.setNodeDiskMountPressureCondition),        withoutError(kl.setNodeReadyCondition),        withoutError(kl.setNodeVolumesInUseStatus),        withoutError(kl.recordNodeSchedulableEvent),    }}

注意上面的setNodeDiskMountPressureCondition这个是我自己添加上面的，不是k8s自带。这个里面包括节点信息、节点OOD信息、内存磁盘压力状态、节点监控状态等。
方法太多，那一个举例子吧setNodeDiskPressureCondition

func (kl *Kubelet) setNodeDiskPressureCondition(node *v1.Node) {    currentTime := metav1.NewTime(kl.clock.Now())    var condition *v1.NodeCondition    // Check if NodeDiskPressure condition already exists and if it does, just pick it up for update.    for i := range node.Status.Conditions {        if node.Status.Conditions[i].Type == v1.NodeDiskPressure {            condition = &node.Status.Conditions[i]        }    }    newCondition := false    // If the NodeDiskPressure condition doesn't exist, create one    if condition == nil {        condition = &v1.NodeCondition{            Type:   v1.NodeDiskPressure,            Status: v1.ConditionUnknown,        }        // cannot be appended to node.Status.Conditions here because it gets        // copied to the slice. So if we append to the slice here none of the        // updates we make below are reflected in the slice.        newCondition = true    }    // Update the heartbeat time    condition.LastHeartbeatTime = currentTime    // Note: The conditions below take care of the case when a new NodeDiskPressure condition is    // created and as well as the case when the condition already exists. When a new condition    // is created its status is set to v1.ConditionUnknown which matches either    // condition.Status != v1.ConditionTrue or    // condition.Status != v1.ConditionFalse in the conditions below depending on whether    // the kubelet is under disk pressure or not.    if kl.evictionManager.IsUnderDiskPressure() {        if condition.Status != v1.ConditionTrue {            condition.Status = v1.ConditionTrue            condition.Reason = "KubeletHasDiskPressure"            condition.Message = "kubelet has disk pressure"            condition.LastTransitionTime = currentTime            kl.recordNodeStatusEvent(v1.EventTypeNormal, "NodeHasDiskPressure")        }    } else {        if condition.Status != v1.ConditionFalse {            condition.Status = v1.ConditionFalse            condition.Reason = "KubeletHasNoDiskPressure"            condition.Message = "kubelet has no disk pressure"            condition.LastTransitionTime = currentTime            kl.recordNodeStatusEvent(v1.EventTypeNormal, "NodeHasNoDiskPressure")        }    }    if newCondition {        node.Status.Conditions = append(node.Status.Conditions, *condition)    }}

方法很简单，核心就是IsUnderDiskPressure，如果是存在压力就把状态改成true，否则改为false。
看完上报的方法，那这个方法是什么是被调用的呢？本能就可以想到，一个是初始一个是定时的更新，下面看看具体是不是这样的，先看初始pkg/kubelet/kubelet_node_status.go里面的initialNode方法

kl.setNodeStatus(node)

这个方法就是调用刚才上面一系列收集状态的函数

func (kl *Kubelet) setNodeStatus(node *v1.Node) {    for _, f := range kl.setNodeStatusFuncs {        if err := f(node); err != nil {            glog.Warningf("Failed to set some node status fields: %s", err)        }    }}

然后就是定时上报，pkg/kubelet/kubelet_node_status.go里面tryUpdateNodeStatus方法，它是定时上报master的方法。

kl.setNodeStatus(node)

它同样调用setNodeStatus这个方法。顺便在多说一句，这个定时上报的方法什么时候被定时执行呢，答案在pkg/kubelet/kubelet.go的Run里面

if kl.kubeClient != nil {        // Start syncing node status immediately, this may set up things the runtime needs to run.        go wait.Until(kl.syncNodeStatus, kl.nodeStatusUpdateFrequency, wait.NeverStop)    }

通过nodeStatusUpdateFrequency指定上报周期，好了关于资源上报的代码很简单，就不赘述了。